THE STEM, OK ASCENDING AXIS. 



33 



velopment of regular buds; and secondly, the production 

 of irregular buds. But although the mathematical order 

 is sometimes thus infringed, the grace and harmony of 

 nature are not impaired. On the contrary, one must 

 feel, in looking at a fine tree however irregular may be 

 its proportions that it must be a daring hand that 

 could attempt an alteration; and the thoughtful mind 

 will recognize in these seeming accidents, only aprofounder 

 wisdom, and a more excellent beauty. 



186. THORNS are abortive branches, which in their 

 dry and undeveloped state become rigid. That this is 

 really the true explanation is shown by their sometimes 

 putting forth leaves, as in the Sloe, fig. 5. Naked 

 thorns, and one clothed with a few leaves, are also seen 

 in fig. 6, which represents a thorny shrub of Palestine. 

 Thorns, prickles and stings, seem to be a kind of natural 

 weapons in plants, and are analogous to the horns, tusks 

 and stings of animals. These, in some cases, disappear 

 under the influence of culture. Hence Linnaeus poetically 

 considers such plants tamed, or deprived of their natu- 

 ral ferocity; and in sober truth, if thorns are really 

 undeveloped branches, there is a very good reason why 

 the higher degree of nutriment found in cultivation 

 should cause them to disappear in the completely devel- 

 oped structure. 



1$7. DISTINCTION BETWEEN A THORN AND PRICKLE. 

 A Thorn is an extension of the wood ; a Prickle is 

 a continuation of the bark only (84), as you may assure 

 yourself by peeling off a small section from the stem of a 

 Rose or Bramble, when the prickle will be removed along 

 with the bark ; but a Thorn treated in the same way 

 shows its connection with the wood. 



188. A TENDRIL is a slender, leafless branch, with 

 a spiral extremity, by which it clasps a firmer body that 

 may serve as a prop. In the Grape, fig. 4, the tendrils 

 take the place of suppressed leaves, from whose axils 

 they arise. They are also branched, as in the Sweet Pea, 

 fig. 8, and thus the means of support are multiplied. 

 The tendrils of the Virginian Creeper will adhere to 

 smooth marble, like the rootlets of Ivy. Sometimes the 

 tendrils belong to the leaves, as in the Pea and the Len- 

 til, fig. 7. 



189. The leaf-buds of many trees are very beautiful in 

 their partial expansion. Among these, that of the Horse 

 Chestnut, which contains both leaves and flowers, is very 

 conspicuous. But the most splendid example known 

 among us is found in the Walnut, the buds of which re- 



Thorns, define. How is this proved? Idea of Linnaeus. Probable Reason. 

 Distinction between Thorn and Prickle. How proved? Tendril, define. 

 Varieties. What buds most beautiful ? 

 5 



semble half-blown Tulips, whose petals have a texture 

 of the richest velvet, varying in color from a delicate 

 flesh-white to a tinge of the finest gold, sometimes relieved 

 and softened by a hue of blush-red, or a tinge of ashen 

 gray. 



CHAPTER XV. 



THE STEM, OK ASCENDING AXIS. 



190. STEM DEFINED. That part of the plant which 

 developes upward, seeking the air and light, is called 

 the STEM ; and in respect to position, it usually has a 

 diametrical opposition to the Root. 



191. DISTINCTIONS OF THE STEM AND ROOT. And 

 between these two organs there are some other quite re- 

 markable differences, which we will briefly notice. The 

 Stem grows by an extension of its whole substance ; 

 the Hoot Ity an application of new material to its ex- 

 tremities. The stem produces buds, and sends forth 

 leaves, and through these chiefly it acts on the element 

 in which it lives. The root gives birth to no organ, 

 but its own parts. With a few remote exceptions, it 

 never produces buds, and therefore bears only naked 

 branches, while it acts directly on the soil, without the 

 intervention of any other organ. The branches of the 

 STEM are symmetrical; those of the ROOT without 

 order. 



192. All phaenogamous plants possess stems, though- 

 in some instances that organ is very short, at others hid- 

 den beneath the soil. The first impulse of growth in the 

 stem is to ascend ; but it does not always preserve this 

 direction, as you will see in the description of subter- 

 ranean stems. 



193. ELEMENTARY COMPOSITION. All very young 

 stems are composed exclusively of parenchyma, or they 

 have only the rudiments of fibre. But in the course of 

 growth various transformations occur, which were treated 

 of in Chapter IV. The most remarkable of these modi- 

 fications is THE PRODUCTION OF WOOD. It will be 



remembered that all the tribes of plants below the Club- 

 Mosses (101), are wholly destitute of wood, and, in all 

 the lowest forms, of every thing like fibre also ; but the 

 humblest plant that is articulated into root, stem, leaf 

 and flower, must have some kind of fibre, or fibre-like 

 tissue, otherwise it could not form the necessary articu- 

 lations and framework of those organs. 



General subject Define Stem. Distinctions of Stem and Koot? Are any 

 of the higher plants destitute of stems ? Of what are very young stems com- 

 posed ? Most important product of transformation. 



